When two panels are to be joined perpendicularly to one another in this manner, e.g. at an L-joint, it is necessary to drill holes in the edge of one of the panels, to drill holes in a large face of the other panel, to push dowels over half their length into the holes made in one of the panels, to bring the other panel into a perpendicular relationship with the first making sure that the holes in the other panel are aligned with the dowels in the first panel, and to insert the free halves of the dowels into the holes made in the other panel. In order to ensure that the panels can be assembled to one another and that the edge of one of the panels lies exactly in the plane of a large face of the other panel, the various holes in the panels must match exactly and must be at a determined distance from the edge of each panel. Any error in measuring or marking the axes of the holes to be drilled makes it impossible to assemble the panels correctly.
Preferred embodiments of the invention provide a jig for locating the holes to be drilled in the various panels and for drilling the holes, with reduced risk of error, and without it being necessary to make prior measurements and markings for locating the axes of the holes to be drilled in the panels.